An image reading apparatus sets an irradiation region below a fixed reading glass when light guide members diffuse light of LEDs upward so that the irradiation region corresponding to a significantly sagged portion in a main scanning direction is wider than that corresponding to portions on both sides of the significantly sagged portion, and sets a light intensity of a plurality of LEDs corresponding to the significantly sagged portion in the main scanning direction to be larger than that of a plurality of LEDs corresponding to the portions on both sides of the significantly sagged portion. Therefore, the degradation of the illuminance corresponding to the significantly sagged portion due to the pressed fixed reading glass can be prevented, and the entire document can be read with uniform reading precision.